Mobile electronic gadgets (such as smart phones, tablets, and laptop computers) are very popular nowadays. These mobile devices provide us with much convenience in communicating with others and accessing online information. Nonetheless, these mobile devices rely on batteries for power storage and normally last only a few hours.
For charging smart phones, tablets and other portable DC-powered loads, detection of supply voltage is not necessary as all these devices are rated at 5 V DC. The universal serial bus (USB) power supply would provide the required charging recognition handshake for smart phones and tablets.
On the other hand, there is no harmonized standard for laptop computer power supply voltage. Laptop computers found in the market have voltage inputs ranging from 9V DC to 20V DC, even though their internal hardware are highly similar. Power supply units for laptop computers are usually incompatible with one another, and laptop computers therefore always come with a dedicated direct current (DC) power supply for battery charging. The output voltage of these dedicated power supplies for laptop computers of different brands and models are different. Therefore, all laptop computers have to be powered/charged by their dedicated power supplies.
With the limited battery storage capacity, dedicated power supply needs to be carried along with the mobile gadget. Depending on the design, their weights range from 0.3 kg to 0.5 kg, and the power density ranges from 6 to 10 W/in3. That adds to the overall burden of carrying the mobile gadgets. Furthermore, the dedicated power supply itself becomes an unnecessary electronic wastage once the laptop computer is abandoned. Although there are available in the market universal power supplies for laptop computers, such require users to manually select the desired output voltage, which is both troublesome and prone to errors.
It is thus an object of the present invention to provide a USB power supply in which the aforesaid shortcomings are mitigated or at least to provide a useful alternative to the trade and public.